The Geography of Drunk Driving

The percentage of accidents involving alcohol varies widely by city.

New Year's Day is consistently one of the most dangerous days of the year for drivers. Not surprisingly, a unusually large percentage of car accidents tomorrow will involve alcohol -- in 2009, alcohol played a role in 40 percent of fatal crashes, as opposed to 32 the rest of the year.

But the geographic distribution of alcohol-related crashes, like their distribution across the calendar, varies widely. "A National Portrait of Drunk Driving," a map created by John Nelson at IDV Solutions' UX Blog, makes this conclusion visually obvious.

Using data from Fatality Analysis Reporting System (FARS), Nelson mapped ten full years of accidents (2001-2010) on a hexagonal mesh of the United States. Each hexagon represents data collected from a roughly identical space with no regard to administrative boundaries. Their color indicates the percentage of accidents that involved alcohol. (The National Highway and Traffic Safety Administration has all data from 1975 onward available for download, for all you data hounds out there.)

Larger hexagons correspond to more accidents -- in the densest areas, the hexagons swell to form a flush surface, whereas in rural areas, the shapes are much smaller. The darker the hexagon, the higher the percentage of crashes involving alcohol.

Above, the percentage of deadly crashes involving intoxication by color. Below, the map:

Evidently, the distribution of hexagons closely resembles the distribution of dots in Brandon Martin-Anderson's Census Dot Map. The more people, the more car crashes.

But the color of accidents is not at all uniform. As Nelson points out, New York City has a very low percentage of alcohol-related accidents, not surprisingly. So do Salt Lake City, Memphis, and Miami (and Detroit and Los Angeles, which are captured on the UX Blog):

Other areas, particularly around clusters of cities, fare less well. The Bay Area and the Pittsburgh-Cleveland-Akron area have a much higher incidence of alcohol-related accidents:

Even in those areas, there are clusters of green on those areas best served by mass transit -- Pittsburgh, San Francisco. But urbanity is no guarantee that people will not drive while intoxicated. Just look at Chicago and Houston (with dishonorable mentions for Denver and St. Louis, pictured on the UX Blog):

Furthermore, just because an area doesn't have a densely settled population doesn't mean it can't have a large number of accidents involving intoxication. See South Carolina:

Explore other U.S. metros, and the full map, over at the IDV Solutions' UX Blog.